1. Field of the Invention
The present invention relates to a power conversion device for a rail way vehicle.
2. Description of the Related Art
A rail way vehicle incorporates a power conversion device wherein speed control of an induction motor that constitutes the main motor is achieved by converting AC power that is supplied from a pantograph to predetermined AC power by a variable voltage variable frequency controlled inverter.
This rail way vehicle power conversion device is assembled in a box that is suspended under the floor of the vehicle; in the interior of this box, in addition to a power conversion unit comprising power semiconductor elements etc, there are accommodated a capacitor that removes harmonic components contained in the main circuit current, and a high-speed circuit breaker and the like provided to isolate the input power source side and the power conversion unit in the event of occurrence of a fault.
Apart from the foregoing electrical equipment, in addition to the capacitor mentioned above, there may also be accommodated a smoothing reactor on the inverter side for suppressing pulsation of the main circuit current and a smoothing reactor on the power source side of this inverter; of these, the amount of heat generated by the reactor, to be described, on the power source side is considerable.
These smoothing reactors may be mounted externally of the box, but the maximum allowed temperature of these smoothing reactors, due to the insulating resin that effects installation between the layers of their internal coils and the frame, is about 180xc2x0; this is higher than that of the semiconductors, capacitors and circuit board of the control device, to be described, etc., which is about 80xc2x0.
As a method of cooling these smoothing reactors and control circuit components, conventionally two methods were adopted, namely, the method of forced cooling using an electrically driven fan (or blower), and the method of cooling using the method of natural convection including the current of air generated by the running of the train.
Of these, the cooling effect of the former i.e. the forced cooling method is high, but the latter i.e. the natural ventilation method is considered desirable on account of the vibration and noise generated by an electrically driven fan, and environmental considerations.
On the other hand, to cope with the continual increase in train speeds, increased capacity and reduced weight of the rail way vehicle power conversion device is demanded and size reduction is also sought, in order to enable this to be arranged in the restricted space under the vehicle floor.
In addition, laborsaving in maintenance and inspection and improvement in the ease of performing the maintenance and inspection tasks are demanded.
Of these, the aforementioned increased capacity and reduction in size and weight and laborsaving in maintenance and inspection are mutually contradictory; measures for cooling the equipment incorporated in the interior of the rail way vehicle power conversion device are therefore becoming increasingly important in order to maintain the prescribed performance in regard to vehicle running over a long period, and to meet these contradictory demands.
However, in conventional rail way vehicle power conversion devices, as regards cooling, devices were easier to manufacture, compared with other electrical equipment, in which a smoothing reactor whose allowed rise in temperature was about 100xc2x0 higher than that of the other electrical equipments ware separately provided.
However, if this was thus separately provided, the amount of space required under the floor for an airflow passage (air dust) for cooling the smoothing reactor and for conductors to effect connection of the power conversion unit connected to this smoothing reactor was thereby increased, complicating the arrangement of electrical equipment under the floor of the vehicle.
On the other hand, in the case of the method in which the smoothing reactor is accommodated in a box together with the other electrical equipment, if this was arranged in series (single air flow system) with respect to the flow path of the cooling air through these items of electrical equipment, the amount of the current of air for cooling the smoothing reactor on the power source side, where the amount of heat generated is largest, must also pass the smoothing reactor on the inverter side, where the amount of heat generated is small; thus the efficiency, taking into account pressure loss, is lowered, making it impossible to meet demands for increased capacity, lighter weight and smaller size.
Furthermore, since the maximum allowable temperatures of these smoothing reactors are the same, the cooling conditions of the smoothing reactor arranged downstream of the smoothing reactor arranged on the upstream side are adversely affected, with the result that its rise in temperature is higher than that of the smoothing reactor on the upstream side.
If, with this in view, the flow paths of the two smoothing reactors are arranged in parallel (two air flow systems), the construction of the flow paths becomes complicated due to these parallel flow paths and due to the baffle plate arranged upstream of these flow paths; this arrangement also therefore cannot meet demands for increased capacity, lighter weight and reduced size and laborsaving in maintenance and inspection.
Accordingly, one object of the present invention is to provide a novel rail way vehicle power conversion device capable of coping with increased train speeds and capable of coping with increased capacity, smaller size and lighter weight as well as laborsaving in maintenance and inspection. A second object thereof is to obtain a rail way vehicle power conversion device wherein vibration and noise can be reduced.
In order to achieve the above objects, the present invention is constructed as follows. Specifically, it consists in a rail way vehicle power conversion device comprising: a power conversion device comprising a semiconductor power conversion cooling unit, a pair of smoothing reactors and a pair of electrically driven fans which cool these; and a box accommodating power conversion device in its interior and suspended under the floor of the vehicle;
wherein an airflow passage of L-shaped transverse cross section is provided, formed with an inlet port on one side in the rail direction of the box;
a semiconductor power conversion cooling unit being accommodated in a region adjacent the airflow passage on one side in the tie direction of the box, with a heat-radiating part thereof projecting on the air inlet side of the airflow passage;
a pair of smoothing reactors being accommodated in the rail direction on the exhaust side of the airflow passage; and
electrically driven fans being arranged at the air inlet side of the smoothing reactors.
By such means, according to the present invention, the flow speed of the cooling air passing through this exhaust path can be lowered and the difference in cooling conditions of the reactors can be decreased, by accommodating the pair of reactors in an exhaust path formed by bending in a direction orthogonal to the air inlet path of the airflow passage.